4
a

erates 1 Heit

[eto

rah
ih ay
i nt)

ist) Hi
oe
sti

aie
Hh
ie i
rag nae
mist chit

Hadi
a.
LEH be a! Os

+ i
ae
Cay aaa a ita
wits a rae sitellt

i uh

th
Hai
Hel ee sa
es
s/f] Sb i th
el ‘oni ni

Any
oe He i Riad

i
YH igi ttt (iets big nae ae
Airy Hie sii ; ‘i fate ia Gets

‘iva

alta tgh ts
anf ts
ies tet
Dt
ce
bay Pa |

iy

Hitiiy

siihts i } of: PF) '
’

deaceck ty
- he. “rt aS
rs eee

hy te et a
it

NATURAL
SURVEY

LIDONAR :

VEY

Digitized by the Internet Archive
in 2010 with funding from
University of Illinois Uroana-Champaign

http://www. archive.org/details/routweedswhywhen28ieho

ae 7 WV’ CG
ne 728 Co

ROUT tk: WEEDS!

med y, WHEN AND HOW

'
ay

Ria et ad ee ae

R.TEHON |
bine,

OTANIST (ites
: a

ILLINOIS NATURAL HISTORY SURVEY
CIRCULAR 28

PUBLISHED BY AUTHORITY OF THE STATE OF ILLINOIS
URBANA, ILLINOIS AUGUST 1937

out the V Veeds
WI LY certain weeds are classed as pernicious.
widespread control measures are needed.
WHE these weeds do the most damage.
control measures are most effective.

HO these weeds cause injury.
to control them.

L. R. TEHON
BoTanlistT

Printed by authority of the State of Illinois
DEPARTMENT OF REGISTRATION AND EDUCATION

NATURAL HISTORY SURVEY DIVISION

Theodore H. Frison, Chief

Circular 28 Urbana August 1937

Pr .

£
N

= SNAKEROOT Eupatorium urticaefolium Reich.
Courtesy New York State Museum, Albany

STATE OF ILLINOIS
Henry Horner, Governor

DEPARTMENT OF REGISTRATION AND EDUCATION

Joun J. Haruman, Director

BOARD OF NATURAL RESOURCES AND CONSERVATION
Joun J. Hatiiman, Chairman,

WiuiiaM TRELEASE, D.Sc., LL.D., Biology
Henry C. Cow tes, Ph.D., D.Sc., Forestry

Joun W. Atvorp, C.E., Engineering

WiLiiam A. Ph. Dz
Chem.D., D.Sc., Chemistry
Epson C. Bastin, Ph.D., Geology

LE: D.,

Noyes,

ArtHur Cutts Wittarp, D.Eng., LL.D.,
President of the University of Illinois

NATURAL HISTORY SURVEY DIVISION

URBANA

ILLINOIS

Scientific and Technical Staff
TuHEopoRE H. Frison, Ph.D., Chief

SECTION OF ECONOMIC ENTOMOLOGY

W. P. Fiint, B.S., Chief Entomologist
C. C. Compton, M.S., Associate Ento-

mologist

M. D. Farrar, Ph.D., Research Ento-
mologist

J. H. Biccer, B.S., Associate Entomolo-
gist

S. C. CHanpier, B.S., Southern Field
Entomologist

L. H. SHropsurre, M.S., Northern Field
Entomologist

W. E. McCautey, M.S., Assistant En-
tomologist

C. W. Kearns, Ph.D., Research Fellow
in Entomology

J. F. AtsTERLuUND, M.S., Research Fellow
in Entomology

Dwicut Powe .t, M.S., Research Fellow
in Entomology

SECTION OF APPLIED BOTANY AND
PLANT PATHOLOGY
L. R. TEnon, Ph.D., Botanist
J. C. Carrer, Ph.D., Assistant Botanist
G. H. Boewe, M.S., Field Botanist

SECTION OF FORESTRY

James E. Davis, M.F., Extension For-
ester

SECTION OF AQUATIC BIOLOGY

Davip H. THoompson, Ph.D., Zoologist

F. D. Hunt, Field Naturalist

D. F. Hansen, A.M., Assistant Zoologist

D. J. ODonneE Lt, M.S., Assistant Zo-
ologist

SECTION OF INSECT SURVEY
H. H. Ross, Ph.D., Systematic Ento-

mologist

Cart O. Monur, Ph.D., Associate Ento-
mologist, Artist

B. D. Burks, Ph.D., dssistant Ento-
mologist

SECTION OF GAME RESEARCH AND
MANAGEMENT ;
R. E. Yeatrer, Ph.D., Game Specialist
W. H. Leicu, M.A., Assistant Zoologist
SECTION OF PUBLICATIONS

CaRROLL CuHovuinarbD, M.A., Editor

This paper is a contribution from the Section of Applied Botany and Plant Pathology

(34017—4M—7-37)
optaramen 2

CONTENTS

Page

HOUSE JOINT RESOLUTION NO. 25..................... RNY at ars key A rch opithe a catch <a ivi
(Adopted May 5, 1937)

EA RENOWN aio) GWU SINGS Sy oe car chscocs nce, ctiehe ana sa Shataue date a fatty eu huasavacas Der diate, eras eros etsrene Gala. loys @re,satie-s tors Seis vi
THEME ORDANCEIOR WEEDS) <oi4 Vie osha sors to cee clers eels oeicie oeeivieis We ve sia seen oes 1
Usefulness of weeds.—Sentiment for weed control.—Noxious weeds.
WEP DSPASTECONOMIG FACTORS aii; ces rok O ac eeern Baaverd 6 6 huey sreleferstale eneret rerare sna t..06 3
Loss to the United States.—Loss per farm.—How weeds cause losses:
poorer yields; expense of growing; poorer quality crops; reduced land

values; livestock poisoning; injury to health.

WEED STASHHARBORERSIOFBN INSECTS 22. 25. cto o oe onic ens Sasi e eet o i orehya knee ws 6 eis 5
Hosts to injurious insects.
ficial parasites.

_

WEEDS AS HARBORERS OF PLANT DISEASES............... Be ere Jn ita cus ovens sacteusushevee Gabe 6
RELATION OFAWEEDS TO! PUBLIC HEALTH ee. 2c. acs se tee fos oe sce heel © sl oste crise © 7
Weed poisons ingested.—Weed poisoning by contact.—Weed poisoning

by spread of pollen.—Relief for hay fever sufferers.

CON TROIMEDHODS a8 sei bros apse ts seek oe noe Creates ota e Te ee Seale 10
Need to know biology of weeds.—Weak stages best control periods.—
Suit control methods to biology: chemical method; fallow method; smother
crops; use of livestock; covering the plants; burning; crop rotation; fer-
tilization.—Three steps in weed control.

BIGHMPERNICIOUS WEEDS) OBRMLEINOIS aac creda oo oie ao lieereiele eos J celle s eleiaie a cies = = US

Common Ragweed, p. 15.—Giant Ragweed, Horseweed, p. 19.—Poison
Ivy, p. 21.—Poison Sumac, p. 23.—Wild Parsnip, p. 25.—White Snake-
root, p. 27.—Pokeweed, p. 31.—Common Burdock, p. 33.

Vv

HOUSE JOINT RESOLUTION No. 25

*

WHEREAS, The wide distribution and prolific growth of weeds
have become an economic loss to Illinois agriculture imposing a burden
thereon estimated at about two dollars per acre and have become one
of the serious problems of agriculture, not only of Illinois but of the
nation; and

WHEREAS, Certain weeds and shrubs, through their irritating
pollens and plant juices contribute directly to ‘“‘Hay Fever’ and plant
poisoning causing discomfort and ill health to thousands of our citi-
zens; and

WHEREAS, Some weeds are unsightly, spoiling somewhat the
beauty of Illinois landscapes and nullifying to a great extent the pro-
gram of highway beautification; therefore, be it

RESOLVED, by the House of Representatives of the Sixtieth
General Assembly of the State of Illinois, the Senate concurring
herein, That the Governor of Illinois is hereby requested to designate
August 8 to August 22 inclusive, as ‘‘Weed Destruction Days’’ and by
public proclamation to enlist the citizens of IIlinois to assist in making
Illinois healthful, clean and beautiful; and, be it further

RESOLVED, That the Director of the State Department of Agri-
culture is hereby instructed to consider the establishment of a com-
prehensive weed control program; specifically to encourage the de-
struction of ragweed, horseweed, poison ivy, poison sumac, wild
parsnip, white snakeroot, pokeberry and burdocks on all public and
private lands, highways and right of ways, and to report to the Governor
of Illinois on or before the 31st day of December 1937, the proposed
and initiated features of such a program.

Adopted May 5, 1937.

Ackno wledgmen ts

*

In the preparation of this circular we have had the cordial cooperation
of Dr. J. J. Pieper, Professor of Crop Production in the University of
Illinois College of Agriculture, Urbana, who has prepared the text on
weeds as economic factors, and on control methods; of Dr. A. C. Baxter,
Assistant Director of the State Department of Public Health, Springfield,
who has furnished the text on the relationship of weeds to public health;
of W. P. Flint, Chief Entomologist of the State Narurat History
Survey Division, Urbana, who has prepared the text on weeds as harborers
of insects; and of Dr. Carl O. Mohr, also of the Narurat History
Survey, who made the drawings for the illustrations of the eight
pernicious weeds which this circular specifically discusses.

ILLINOIS NATURAL
HISTORY SURVEY

eG CIRCULAR 28

AUGUST 1937

8 Pernicious Weeds of Illinois,
L. R. TEHON pictured and described for your
Broitracne1 sit participation ina statewide cam-
paign of eradication.

WHY © WHEN « HOW

The Importance of Weeds

Ey ERY person who deals with plants sooner or later makes
his own definition of a weed. When civilization was young, a
weed undoubtedly was any plant that could invade man’s
crudely cultivated fields, increase faster than his own none too
energetic efforts at cultivation could keep it down, and en-
danger his existence by threatening his harvest. With time
much has been learned about plants, and the meaning of the
term has been extended to include plants with other evil effects.
Today any plant that, for any reason whatever, is a nuisance
to mankind may be called a weed. Plants that do not grow in
cultivated fields but which harbor insects or diseases destruc-
tive to crops are regarded as weeds. Plants that carry the
menace of ill health to individuals because of their ability to
cause mild or severe kinds of poisoning are commonly looked
upon as weeds. And still other plants that threaten, during
short or long seasons, the health of individuals or communities
because of their pollen or because of poison transmitted in milk
are considered very dangerous weeds. There are, also, plants
whose greatest crime is that they merely inconvenience man in
his daily life, and these likewise are weeds.

Usefulness of Weeds.—The fact that in some respect a plant may
be enough of a nuisance to humanity to be classed as a weed
does not mean that the plant is without usefulness. It has been
said that the greatest usefulness weeds have is that they are
weeds. Their universal presence and their habit of springing
up year after year necessitates tilling the soil, and tillage con-

[1]

2 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 23 AUGUST

tributes to profitable yields. The cover of weeds and wild
plants that springs up on land after a crop has been harvested
in midsummer gives protection against blowing of the soil by
winds and washing by floods, and the green material, plowed
under again as green humus, returns fertility to the soil.

Among the weeds described in the following pages, Common
Ragweed stands preeminent in this respect, for its universal
abundance in harvested grain fields during late summer gives
it title to the description, ‘‘most abundant weed in the state.”
Both it and Giant Ragweed furnish cover and food for game
birds in late fall and winter, at a time when other food is scarce,
and the survival of natural game such as prairie chickens and
quail in certain parts of our state is very possibly due to the
food furnished at critical times by these plants. Pokeweed,
notwithstanding that it harbors and provides a means of over-
wintering for the very destructive mosaic disease of cucumbers
and muskmelons and that its berries and roots contain a poison,
furnishes a drug which has been used extensively in alleviating
certain human pains. Moreover, young Pokeweed shoots may
be cooked and eaten like asparagus. Even Great Burdock and
its much more abundant relative, Common Burdock, ugliest
plants, as many think, of the countryside, furnish roots and
seeds of medicinal value, and in Japan the Great Burdock is
cultivated for its roots, which are eaten as a vegetable.

Sentiment for Weed ControlBecause today weeds intrude into
so many of man’s affairs, their importance is more thoroughly
appreciated than ever before. This appreciation has made
itself evident both in the recent revision of the Illinois weed law
to include European Bindweed as a noxious weed along with
Canada Thistle and Perennial Sow Thistle, and in Joint Resolu-
tion No. 25 of the Illinois House and Senate which requests the
Governor to designate a period of the year as “‘Weed Destruc-
tion Days’’ and instructs the Director of the State Department
of Agriculture specifically to encourage destruction of the weeds
described in the following pages.

This pamphlet has been designed and printed as a contri-
bution both to the general problem of weed control and to the
specific task imposed by the legislative resolution, which appears
facing page 1. The pictures and descriptions which follow
are intended to aid in identifying these weeds, and the accounts
of their distribution and habitat, their blossoming and seeding

1937 TEHON: ROUT THE WEEDS! 3

times, their biological interest, and methods of control are in-
tended to make available to the people of this state information
which will enable them to protect themselves against the
dangers, both direct and indirect, that these weeds present.

Noxious Weeds.—Canada Thistle, Perennial Sow Thistle and
European Bindweed are noxious weeds, the destruction of which
is required by law. Because of their great importance in agri-
culture, the Illinois Agricultural Experiment Station and Ex-
tension Service has undertaken investigations bearing upon their
life history and control, maintains projects for their control
in rural areas in cooperation with farm bureaus and the State
Department of Agriculture, and intends to issue a compre-
hensive publication concerning them.

Weeds as Economic Factors

The actual loss from weeds is not known. There are but few
experiments which give a basis for an intelligent estimate. An
experiment which was completed a few years ago at the Illinois
Agricultural Experiment Station shows that the yield of corn
was reduced about 80 per cent by omitting cultivation and
permitting the weeds to grow. The Michigan Agricultural
Experiment Station came to the conclusion that they cultivate
sugar beets primarily because of weeds. In the case of potatoes
they found that quack grass cut the yields of potatoes from one-
half to two-thirds. At one of the Canadian experiment fields
Russian thistle seed was sowed with wheat and observed to cut
the yield 40 per cent.

A common but conservative estimate of the loss to agri-
cultural products by weeds is 10 per cent. At times this has
reached a billion dollars for the United States.

Loss to the United States—The Agricultural Service Department
of the U. S. Chamber of Commerce, in a report submitted to
the Federal Farm Board, estimated the weed loss to agricul-
ture at 3 billion dollars. At that time this would have been
equivalent to about 30 per cent of the value of all agricultural
products.

Loss per Farm.—In 1930 Indiana estimated the weed loss per
farm at $210 and Wisconsin in 1927 put the figure at $244 per
farm.

While actual figures, as a basis for an intelligent estimate of
weed loss, arescarce, yet they are sufficient to show that the amount

4 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

is enormous. Because of the rapid spread of weeds, one close
to the subject would conclude that weed damage is increasing.

How Weeds Cause Loss-—The major ways in which weeds cause
loss are (1) reduction in crop yields, (2) increase in expense of
growing the crop, (3) decrease in quality of the product, (4)
reduction in the value of the land, (5) poisoning livestock, and
(6) their relation to public health.

PoorER YIELDS.—Weeds reduce crop yields by utilizing plant
food materials and moisture in the soil, and by shading the
plants. A weedlike dodder reduces crop yeilds by being para-
sitic upon the host plant from which it draws its nourishment.

EXPENSE OF GrowiInc.—It is all too evident that weedy lands
require extra cultivation and considerable hand work to keep the
weed loss to a minimum. Weeds such as vines interfere with
tillage and harvesting operations, while often weedy seeds and
grain must be cleaned before they can be put on the market.

PoorER Qua.Lity Crops.—The quality of many agricultural
products is on the downward trend because of weeds. For exam-
ple, the loss to small grain in dockage alone in four spring wheat
states has about doubled in 25 years and is now estimated at
more than 8 million dollars. The loss to winter wheat from wild
onions and garlic is increasing and is estimated at one-third
of a million dollars in southern Illinois. When we consider, in
addition to these, the lower grades in hay, wool, milk and other
animal products, we can see that weeds lower very definitely
the quality of our agricultural products.

REDUCED Lanp VaLuEs.—That the value of land is being ma-
terially affected by noxious weed infestations is noted from re-
ports of loan companies who reduce the appraised value of the
land from one-third to one-half because of weeds. The reduction
is often equivalent to the cost of eradication. No one wants a
weedy farm, and in some cases weeds have forced abandonment
of the land for agricultural purposes. The enormous rate at
which agricultural land is becoming infested with noxious weeds
has lead to definite weed projects by many agricultural experi-
ment stations.

LivEsTock Potsoninc.—In the United States the loss of ani-
mals from poisonous plants is estimated at 15 million dollars an-
nually and for Illinois one million dollars. A few animals dying
here and there go almost unnoticed, but the total for any one
state or region mounts to a sizeable sum.

1937 TEHON: ROUT THE WEEDS! 5

Injury To Heattu.—The effect of weeds on public health is
definite and in many cases serious. Discussion of this injury
is given on page 7.

Weeds as Harborers of Insects

The eight weeds described in this circular—Common Rag-
weed, Ambrosia elatior; Giant Ragweed or Horseweed, Ambrosia
trifida; Wild Parsnip, Pastinaca sativa; White Snakeroot,
Eupatorium urticaefolium; Pokeweed, Phytolacca decandra; Poi-
son Ivy, Rhus radicans, Poison Sumac, Rhus Vernix; Common
Burdock, Arctium minus—have some effect on the abundance
of injurious insect species.

Hosts to Injurious Insects Probably the most important way in
which these weeds influence the abundance of injurious insects
is by acting as hosts for certain of these insect pests. Wild
Parsnip is apparently relished by the worms of the carrot
swallowtail just as much as are carrots and parsnips in the gar-
dens. It is certain that this weed does aid in maintaining an
abundance of these caterpillars. Poison Ivy in orchards acts as
a host forcertain leafhoppers that also attack apple. A distinct
connection has been noted between the abundance of poison ivy
under the apple trees and the number of leafhoppers found on
the trees. Leafhoppers are generally more abundant in apple
orchards where poison ivy is common. Burdock is a highly
favored food of young grasshoppers, and also acts to some ex-
extent as an alternate host for the rhubarb curculio. Ragweed,
particularly the Horseweed or Giant Ragweed, is one of the
most highly favored hosts of the common stalk borer. This weed
certainly acts as a reservoir for the stalk borer, and more of
these borers are produced in the Giant Ragweed than in culti-
vated crops. However, the borer will work in so many other
hosts that the ragweed cannot be considered particularly im-
portant in maintaining this species.

Shelter for Injurious Insects—Another way in which weeds act
as protection for insects is by affording winter shelter for them.
None of the weeds mentioned is of particular importance in this
respect. Adults of the southern corn rootworm are very common
on Wild Parsnip in late September and October, and probably
some of the adults of this beetle hibernate in the Wild Parsnip
leaves. Poison Ivy affords hibernation shelter to a considerable
number of insects, including leafhoppers, chinch bugs and flea

6 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

beetles. The eggs of the common stalk borer are frequently
carried over the winter on the stems of ragweed.

Hosts to Beneficial Parasites—Another relationship between weeds
and insects is, on the whole, beneficial to the farmer. In it,
insects that normally live entirely in weeds, such as certain
borers in ragweed, act as alternate hosts to parasites which also
prey on injurious insect species. A borer in ragweed acts as an
alternate host to parasites of the Oriental fruit moth. This is
a rather important relationship and in several cases important
parasites can only be maintained in areas where an insect
normally infesting weeds serves as the alternate host. In this
respect, weeds are a decided aid in keeping down injurious in-
sect species.

Weeds as Harborers of Plant Diseases

From time beyond memory weedy fields have symbolized
the poverty that is the result of idleness and neglect. And
sanitation, foremost among measures advocated to maintain
the public health, has been symbolized by the trim neatness
of homes and fields free of weeds.

Weed eradication is as important in the protection of valu-
able plants from attack by disease as it is to public health. And
not infrequently it happens that in the eradication of a weed
for the protection of human health, the same purpose is served
for plants of economic value.

Bacteria capable of causing serious diseases of certain crop
plants are harbored by weeds that grow in the fields or on ad-
jacent land. Parasitic fungi, by which the majority of plant
diseases are caused, very often are capable of attacking weeds
as well as valuable plants, and weeds or other native plants are
necessary, as alternate hosts, to the persistence of certain fungi.
The viruses that cause mosaic diseases of plants often have
wide host ranges and are able to attack many wild and weedy
plants as well as important crop plants.

Of the weeds described in the following pages, Wild Pars-
nip is subject to attack by a fungus that is parasitic also on
cultivated parsnip and celery and often does much damage in
celery beds. Pokeweed is one of the wild hosts of the virus
that causes the destructive mosaic disease of cucumbers, and
the virus finds in the large roots of Pokeweed an excellent
place in which to overwinter.

Bacterial and fungous diseases are transmitted from weeds

1937 TEHON: ROUT THE WEEDS! 7

to cultivated plants by winds, by splashing and running water,
and by insects. In the case of virus diseases, transmission by
insects is especially common. Weed eradication becomes the
more important because, in addition to the damage weeds
themselves do, they present the interrelated problems of dis-
ease control and insect control.

Relation of Weeds to Public Health

Weeds constitute a public health problem as well as an
agricultural one. Many weeds contain poisons which if in-
gested by man cause severe illness and sometimes death; others
may cause external injury to certain individuals, while still
others produce pollens which are responsible for hay fever and
similar asthmatic conditions.

Weed Poisons Ingested.—A number of cases of accidental poison-
ing due to the substitution of poisonous plants for similar plant
foods have been reported. Water hemlock has been mistaken
for its harmless relative sweet cicely, or for artichokes or parsnips
in the early spring, the tubers being especially tempting to
children because of the sweetish taste. Wild parsnip, likewise,
has produced death because of its similarity to garden parsnips.
Fool’s parsley, an acridly poisonous plant, is sometimes con-
fused with true parsley. Children sometimes mistake the
poisonous narrow-leaved laurel for young wintergreens. Also
they may chew the fruit of black nightshade and pokeweed or
the seeds and flowers of jimson weeds. Severe illness may be
caused by the ingestion of corn cockle seeds which have been
ground with wheat flour.

Cases of milk sickness occur practically every year in Illinois
and have been attributed to the use of meat and milk products
from animals which have been eating white snakeroot. The
substance believed to be responsible, trematol, is destroyed only
very slowly by boiling; therefore pasteurization of milk is of
little value in safeguarding against it. Milk sickness appears
to result from the continued use of products from affected cows
rather than from the occasional consumption of a small amount.
This fact probably explains the occurrence of the disease in
rural families and its absence in cities. The progress of the
disease is rapid and the mortality high, for at the present time
there is no satisfactory treatment. Extermination of white
snakeroot and avoidance of the use of milk from affected cows
are the only means of combating the malady.

8 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 23 AUGUST

Weed Poisoning by Contact—-A number of plants cause distress-
ing symptoms when they come into contact with the human
skin. Poison’ivy and poison sumac are the most frequent
offenders. Even the slightest trace of the poisonous principle,
toxicodendrol, in these plants will produce blotching of the
skin and itching and burning sensations which may be followed
by the appearance of small vesicles that run together and form
blisters. Complete immunity to ivy poisoning probably does
not exist. Many persons who have believed themselves to be
immune have had serious cases of poisoning after handling
the plants carelessly. Some persons, however, are much more
susceptible than others and occasionally a fatal case has been
reported. Actual contact with the plant is not always necessary
for a case of poisoning—shoes, clothing, utensils and even
animals may carry the poison to an exceedingly sensitive person.

After exposure to the plant attempts to remove the poison
should be made immediately. Three to four thorough scrubbings
with alkali soap and repeated rinsing in running water may be
sufficient to protect the skin from irritation. Special attention
should be given to finger nails and the skin between the fingers,
for careless washing serves only to spread the poison. Space
will not permit a list of the various remedies which have been
recommended for ivy poisoning, but if a case is severe one should
consult a physician rather than spread the infection by using
a trial and error method with home remedies.

Juice of the leaves of Snow-on-the-mountain, Painted Leaf
and several other members of the spurge family as well as that
of Smartweed and the roots of Cow Parsnip are also capable
of causing irritation and blistering of the skin.

Weed Poisoning by Spread of Pollen—The weeds which cause the
greatest amount of misery, however, are those which produce
pollen causing hay fever. It has been estimated that 1 to 4
per cent of the population of the United States suffers annually
from some form of this disease.

Hay fever is characterized by catarrhal attacks of the mucous
membranes of the upper respiratory tract and conjunctiva, due
to a special sensitiveness to pollen from one or more plants.
It may range in severity from mild attacks similar to a cold to
severe and persistent asthmatic attacks. Some sufferers feel so
wretched that they are forced to leave their work and go toa
region where plants causing their illness do not exist.

1937 TEHON: ROUT THE WEEDS! 9

There appears to be a tendency for hay fever to become
hereditary. If both mother and father have hay fever their
children are apt to be afflicted early in life. About one third of
all hay fever sufferers show their first evidence of this ailment
before 10 years of age and two thirds before 25 years of age.
In other words, the great bulk of these people will be burdened
throughout the most important years of their lives with a
serious handicap.

Formerly it was believed that plants producing the most
showy flowers were responsible for hay fever, but H. M. Hall,
California, has pointed out that this is seldom the case, for
pollen produced by large or showy blossoms is almost always
insect carried and is

therefore, relatively heavy and not produced in great abundance.

On the other hand, most plants with small inconspicuous flowers

are wind pollinated; their pollen is therefore light and produced

in great abundance, and it is this voluminous, light-weight

pollen that reaches the nostrils of susceptible people and causes

the trouble. The patient, noticing the showy flowers of a

neighbor’s orchard trees or ornamental shrubbery, is likely to

hold these responsible for his hay fever, whereas the cause is
more likely to be the homely, neglected weeds of the roadside

or of his own back yard.

There are three principal hay fever periods. The first occurs
from April to June when the chief pollens are those from trees,
such as oak, elm, birch, hickory and maple. The second over-
laps the first, beginning about the end of May and extending
to the middle of July; the chief pollens during the period are
those from grasses, such as timothy, redtop, June grass, blue-
grass and orchard grass. The third period is the most important
and extends from the middle of August to frost. It is during
this period that the injurious weeds, such as ragweed and its
near relatives, pollinate. Approximately 85 per cent of cases
are susceptible to ragweed, therefore the majority of cases
occur in the late summer and autumn.

Pollen may be carried long distances by air currents. After
storms pollens have been found 400 miles from their source.
O. C. Durham, of North Chicago, has made a survey of ragweed
pollen incidence in 22 cities in the United States. Of these cities,
Oklahoma City, Okla., was represented as having the highest
average daily ragweed pollen concentration, 814 pollen granules
per cubic yard of air, while Ann Arbor, Mich., was second high-
est with an average of 590 granules. Chicago’s average was given

10 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

as 115. Since only 25 granules per cubic yard of air are necessary
to produce symptoms of hay fever in susceptible persons, one
ragweed plant, which may throw out into the air as many as a
million million pollen grains in one season, may cause a great
deal of distress.

Skin tests are valuable in determining which pollens are
toxic to an individual. An extract of the suspected pollen is
either placed on a scarified area of the skin or injected between
the layers of the skin. A marked reddening surrounding the point
of inoculation indicates sensitivity to the pollen which was
used for the test.

Relief for Hay Fever Sufferers——In many cases immunization may
be accomplished by repeated subcutaneous injections of ex-
tracts of the offending pollens in increasing doses. This treat-
ment must be started at least six weeks before the onset of the
disease if good results are to be obtained.

Filtration of the air of homes and workrooms and air con-
ditioning will remove pollens and afford relief for hay fever
sufferers but obviously people cannot live for weeks within the
protection of these rooms. The only means of affording permanent
relief for these victims 1s the eradication of all varieties of weeds
which are common causes of hay fever—a stupendous task which
would require the combined efforts of city, state and federal
organizations, but one which would be well worth undertaking.
Not only would physical relief be given to thousands of hay
fever sufferers, but also many of the farmer’s worst enemies
would be destroyed, vacant lots and roadways be cleared of
unsightly areas and a number of cases of poisoning would be
prevented. Schools, clubs and other local organizations would
be of enormous value in educating people to cut or otherwise
destroy weeds before they produce pollen.

Control Methods

Practices involved in good husbandry are those for the most
part which contribute to weed control and eradication. After
noxious weeds have once been introduced to the farm then a
knowledge of the character and habits of growth of the in-
dividual species is important in effective control and eradica-
tion.

Need to Know Biology of Weeds.—It is necessary that one know
the life history of a species, namely whether it is annual, winter
annual, biennial or perennial; also its means of reproduction,

1937 TEHON: ROUT THE WEEDS! 11

whether it be by seed alone or seed and some vegetative means,
such as stolons, rhizomes, bulbs and cuttings or by vegetative
means alone. Knowledge of the natural requirements of the
plant is also essential. Some weeds, for example, are character-
istic of wet lands, sandy soils, cool climates or humid climates.
Likewise certain weeds seem to be very definitely associated
with certain crops. For example, Corn Cockle and Cheat are
associated with winter wheat; Wild Mustard and Pennycress
with oats; Red Sorrel and Ironweed with pasture lands; Oxeye
Daisy and Whitetop with grass meadows; Buckhorn and Curled
Dock with red clover; and Lamb’s Quarter and Buttonweed
with corn.

Weak Stages Best Control Periods.—All weeds have weak stages in
their life history at which time they are most effectively con-
trolled or eradicated. Most plants are weak in the seedling and
reproductive stages. The farmer takes advantage of this
knowledge and tries to eradicate as many weeds as possible in
the seedling stage during seed bed preparation and the early
cultivation of the crop. Mowing pastures and waste places
when weeds are blooming is another example of man taking
advantage of this weak stage in the life cycle of the weed plant.

Suit Control Methods to Biology—Methods of eradication of weeds
may be put into two classes depending upon the means of prop-
agation. Weeds which propagate by means of seeds as do
annuals, winter annuals and biennials, are best controlled by
preventing seed production. This is accomplished easily by
killing the weeds in the weak germination and seedling stages
through cultivation, by mowing when the plants are in bloom
but before seed are produced, by plowing shortly after the crop
has been removed, and by use of cheap chemical sprays on
untilled land.

Weeds which depend in part or entirely upon vegetative
reproduction can be controlled only by preventing top growth
from making its appearance above ground. This may be ac- |
complished by destroying the entire plant either with chemicals
or some cultural practice, or it may be accomplished by starv-
ing the roots by cutting top growth and thus preventing manu-
facture of plant food in the leaves.

The means employed to bring about satisfactory control
or eradication of weeds are (1) the chemical method, (2) the
fallow method, (3) smother crops, (4) use of livestock, (5)

12 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

covering of the plants, (6) burning, (7) practice of a good rota-
tion and (8) fertilization of the land.

Cuemicat Metuop.—There are three classes of chemicals which
may be used: (a) those which burn down top growth, (b) those
which sterilize the soil for long periods, thus killing all plant
growth, and finally (c) those which sterilize the soil temporarily.

Iron sulfate, copper sulfate, sodium arsenite and sulfuric
acid are examples of top burners. Iron sulfate and copper sul-
fate are used to kill broad-leaved weeds in lawns, pastures and
grain fields. These chemicals do very little injury to grasslike
plants but will kill legumes and broad-leaved weeds. Sodium
aresenite and sulfuric acid will kill all top growth. The former
is used by railroads and highway departments to burn down
top growth and thus kill the weeds which propagate by means
of seeds. None of these chemicals will kill perennial weeds
unless it is applied often enough to starve out the roots by
preventing food to be manufactured in the leaves.

In the second group of chemicals are salt and heavy oils.
When these are applied to the soil in large enough quantities
the soil is rendered sterile. They should not be used on agri-
cultural land or where one wishes to grow plants in the future.
Such chemicals find their best use on drives, walks, tennis
courts, and about lumber yards and manufacturing plants.

Chlorates, such as sodium chlorate, calcium chlorate and
magnesium chlorate, represent the third group of chemicals.
When these are applied to the soil they render it sterile for six
months or a year but during this time the chemical disintegrates
and finally leaves the soil fertile as before. Chlorates not only
kill top growth but penetrate the soil and kill root growth.
This group of chemicals is the most satisfactory for the eradica-
tion of perennial weeds which propagate vegetatively either
entirely or in part.

Fattow Metuop.—The fallow method is used in the main to
eradicate noxious perennial weeds which propagate vegetatively.
The method consists of plowing the land followed by thorough
discing so as to cut up the root stalks in pieces as fine as possible
and at the same time to prepare a good seedbed. As often as
the weeds begin to show growth above ground, they are cut
off underground by means of a weed cultivator or some other
implement which will do a good job. These cultural operations
are repeated every week or 10 days or as often as new growth

1937 TEHON: ROUT THE WEEDS! 13

shows itself. If at any time cultivation will not kill all top
growth, the land should be plowed again somewhat deeper than
the first time, followed by the weed cultivator as before. Late
in the fall the land should be plowed deep. The next spring the
cultivation should be renewed and continued until late spring
or early summer, at which time a rank growing crop should be
seeded. Most of the weeds should be killed but if this should
not prove to be true, the land should be plowed and the culti-
vation continued.

The object of the fallow method is to starve the roots by
drawing upon their food supply to produce new shoots and at
the same time prevent leaf formation and the manufacture of
food. The fallow method is most effective upon shallow-rooted
perennials where one is able to plow up the root-stalks and cut
these into small pieces. For each small piece to live, it must
send up a new shoot. The food supply in small pieces is soon
exhausted and the root compelled to die.

Deep-rooted perennials require a much longer period of
fallowing since their food storage cannot be divided into small
pieces by disking.

SMOTHER Crops.—There are very few weeds which are eradi-
cated by smother crops. Canada thistles may be eradicated by
seeding alfalfa on the land after it has been well fertilized and
prepared. Most perennial weeds are weakened by smother crops,
thus making the fallow method easier. Hemp and soybeans
are Other good smother crops.

Use or Livestocx.—Livestock such as goats and sheep is often
used to graze weedy land in the hope that the animals will keep
the weeds eaten off close to the ground and thus starve out the
roots. This method is effective providing the animals can be
induced to eat the weeds and providing they are grazed over a
period of years. Most weeds are not relished by grazing animals.
Grazing is most helpful when used in combination with other
methods.

CovERING THE PLants.—Small areas of weeds may be eradi-
cated most cheaply by covering with a heavy paper so as to shut
out all light to prevent growth. Tar paper or heavy building
‘paper will be satisfactory. The paper must be lapped sufficient-
ly, and weighted down so that the plant will not grow between
the sheets. Straw has been used as a temporary covering and
then burned off as soon as the plants make their appearance

14 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

through the straw. Straw stacks and sawdust have also been
used to cover weed patches with varying degrees of success.

Burninc.—While it is not good farm practice to burn organic
matter in the form of crop residues on agricultural land, yet
occasionally one must choose between the destruction of organic
matter and the eradication of some weed pest. There is less
objection to burning waste places for the destruction of weeds.
Where a noxious weed exists and mowing and burning will
destroy seed production and the resultant spread of the plant,
it is to be recommended until more definite eradication methods
can be put into practice. Several kinds of weed burners are
manufactured to be used for fence rows and other places not
accessible for other means.

Crop Rotation.—A well-designed crop rotation will go a long
way to control and eradicate weeds. The one or two-crop
system is most conducive to the weedy farm. Cornfield weeds,
for example, thrive and spread best by continuous growing of
corn or some similar crop on the same piece of land. On the
other hand grain-field weeds are kept under control by putting
the land to a cultivated crop like corn, soybeans or potatoes.
Even pasture has its place in a well-designed rotation as far as
weed control is concerned. When pastures become highly infest-
ed with their characteristic weeds nothing is more practical in
their control than to put the pasture land to a cultivated crop.

FERTILIZATION.—The fertilization of pastures and meadows is
an accepted method of weed control. Where the turf is heavy
annual weeds cannot become established. A dense growth of
any grain or forage crop makes it difficult or almost impossible
for most weeds to become established. Poor stands and poor
growth are almost sure to be associated with an abundance of
weeds. Where legumes are successfully grown limestone and
phosphorus are necessary and without these we end with a
weed patch. Marked reduction in the amount of weeds in
clover and alfalfa fields has been recorded as a result of applying
different fertilizers.

The weed-free farm or garden does not exist, so that the best
that one can hope to do is to eradicate the most noxious weeds
and control the others to such an extent as to reduce the loss
from weeds to a minimum.

Three Steps in Weed ControlOnly pure weed-free seeds should be
sown, since nearly 75 per cent of our worst weeds are not native

1937 TEHON: ROUT THE WEEDS! 15

in the United States but have been introduced in impure seed.
Weedy hay and commercial feed often introduce new weeds to the
farm. We should stop traffic in weed seeds to and from the farm.

Preventing weed seed production on the farm by every
method adaptable to the situation at hand is the second most
important step in reducing the weed loss.

The third step is to design some program of eradication for
the most noxious weeds and to carry it out in every detail.

Eight
Pernicious Weeds
of Illinois

e
COMMON RAGWEED Ambrosia elatior L.
GIANT RAGWEED. HORSEWEED Ambrosia trifida L.
POISON IVY Rhus radicans L.
POISON SUMAC Rhus Vernix L.
WILD PARSNIP Pastinaca sativa L.
WHITE SNAKEROOT Eupatorium urticaefolium Reich.
POKEWEED Phytolacca decandra L.
COMMON BURDOCK Arctium minus Bernh.

e

COMMON RAGWEED

Ambrosia elatior L.

Appearance-—Common Ragweed, less frequently known as
Bitterweed, Roman Wormwood and Wild Tansy, is a freely-
branching herb that grows 1 to 3, or sometimes 5, feet high.
Its hairy green stems and branches bear many finely divided,
feathery, thin leaves, deep green on the upper surface and pale
beneath, and in late summer end in long spikes of green flowers
dusted with yellow pollen. There is, however, a second kind of
flower. It produces seed and occurs singly or in clusters nearly
hidden in the angles between upper leaves and the stem. The
tiny seeds, which are sledom seen, are encased in hard fruits.
These fruits, only about an eighth of an inch long, are grain-
like, somewhat top shaped, beaked at the tip, and crowned with
4 to 6 spiny points. Common Ragweed is an annual plant which
springs up each year from seed.

16 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

‘Ns Y
v N
NI iS \)
N \ Y Vy
\ Ny N} NN) (
SW Vi NY Ny
= \Y W
=, Wit

SSF saaN NY, \ VW)
Zp tS )
Mi Ges Z, ea x . y }

SS NK

rN

A

= ee SSS

SS WIS

; 5 AS IW Nis

1S \ QV \\YSs>
a‘ INS
= |

BNI S ENF
= NG? YEE. f) {
EN

, aN ‘& VPN AX IN
fa ¥ eet AN ‘

y = A ~
t-. Ni ~ pP
Y : a,
a a \ 4 YEE
= \ ji
= 5 EG Lif
(> a ZB
> f 2
Ve Zz
Wand =
L¥Y 5

[2S
ow

{ ye

COMMON RAGWEED Ambrosia elatior L.

1937 TEHON: ROUT THE WEEDS! 17

Distribution Common Ragweed is an American plant with a
natural range that extends across Canada and throughout most
of the United States. It grows everywhere in Illinois and is one
of the commonest weeds in the state. Its importance is due
chiefly to its pollen, which is the main cause of hay fever in late
summer. After harvest it springs up in stubble, often in stands
as pure as though it had been planted. In meadows and pastures
it often is a pest, and in cities, towns and villages every area
of land not thoroughly sodded with grass or cleanly cultivated
is certain to harbor a number of plants. Cattle, lacking better
food, will eat it, and if it is mixed with clover, alfalfa or hay
the bitterness of its juice causes a bitter taste in milk.

Biology.—The flowering period of Common Ragweed usually
begins about the first of July in the southern part of Illinois and
about the first of August in the northern part. But pollen does
not become abundant enough to cause severe hay fever for two
to three weeks after blossoming starts. The blossoming period
continues until September or later, but after August pollen
production usually is not sufficiently heavy to cause severe hay
fever. Seeding time ranges from about the first of August in
southern Illinois and the middle of August in northern Illinois
until frost. Ragweed spreads and reproduces entirely by means
of its grainlike fruits. These are borne in great numbers and
are very easily distributed with harvested grains and by wind.
When buried in the soil, they retain their vitality for years.

Control—Control measures for ragweed have two purposes:
first, to prevent pollen production in and near populous areas
so as to control hay fever, and second, to destroy the weed in
agricultural regions because of its pernicious habits. When the
plants are young, the thin widespreading foilage is easily killed
by copper sulfate or iron sulfate solutions. These solutions
are not harmful to grasses and may be used both on farms and
in cities. Enforcement of laws requiring cutting of weeds on
vacant and neglected lots, if done when the plants start blossom-
ing, tends to control the pollen nuisance. Cultivating stubble
immediately after harvest kills plants already up and encourages
germination of seeds in the soil, which may be killed later with
the harrow, although this is contrary to good farm practice.
Mowing pastures, grain fields, and clover fields to prevent
Ragweed from blossoming and setting fruit is especially im-
portant, and eventually accomplishes the same purpose.

AUGUST

ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28

18

(]
2
YON
a3
Ley
a ow

\

La

\WWithod
Bis

WSS

ie
Sx <—— ¥

—LLZ ys Nee

——
<>

= SSE his

x
iy
Y\

4)
MK
ry

ii

Y
=

\)

\

é \\ Y/

SK |g x = y
NIWA Sy T ee
\ a ERT OBER Z
f \) \ i \ dt a fS oe = we lee pfss =
y SS Snes Oe Mg me tes

Ambrosia trifida L.

HORSEWEED

GIANT RAGWEED.

1937 TEHON: ROUT THE WEEDS! 19

GIANT RAGWEED. HORSEWEED
Ambrosia trifida L.

Appearance.—Giant Ragweed, frequently known also as King-
head and Horseweed, is a huge, coarse herb that grows 4 to 6
feet high and not uncommonly to 10 or 15 feet. Its upright,
stout woody stem, covered with rough and bristly hairs, branches
widely and bears oppositely placed leaves that often are a
foot long or more, rough and hairy like the stem, 3-nerved,
commonly divided into 3 large lobes, and coarsely toothed.
Flowers are of two kinds. Those that bear the pollen are closely
crowded on the straight or branched leafless tips of the main
stem and branches, forming pollen-dusted green spikes some-
times more than a foot in length. The seed-bearing flowers,
their clusters hidden between leaf stalk and stem in the upper
part of the plant, are not often noticed. The brownish, top-
shaped, ribbed, seedlike fruits, about three-eights of an inch
long, end in a short beak and are crowned just below this with
a ting of 5 or 6 short spines. Giant Ragweed is an annual and
is propagated only by seed.

Distribution—Giant Ragweed is native, ranging from Nova
Scotia across Canada to Manitoba and southward to Florida and
Mexico. In Illinois, it ranges throughout the state. Although natu-
rally a plant of stream banks and shores, it has adapted itself suc-
cessfully as a weed and has become established in the country, in
towns, and in cities wherever moist soil is available. It is abun-
dant along streams, ditches, fence rows and neglected roads.

Biology.—Blossom time for Giant Ragweed begins about the
middle of June in southern Illinois and early in July in northern
Illinois and extends into September. The terminal shoots that
bear the pollen-bearing flowers are.so.numerous, so long, and so
thickly covered with flower heads that this plant adds materially
to the ragweed pollen content of the air during hay fever time.
Where it grows as a weed, its growth is so rank above ground
and so extensive below ground that other plants are com-
pletely crowded out or starved. Its hard, light fruits, in which
its seeds are borne, are produced in great abundance and are
distributed with agricultural seeds, blown about on frozen soil
and snow in winter, and carried long distances by streams.
From October through December its fruits are an important
part of the food of game birds. The seeds in buried fruits re-
main alive for several years.

26 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

—

<SS SSS S
Sd SY : SS
SSX

SLY \ \)

WOW

VS

=
S

NS

\ Be = 4
[ASS LG
AWG, i

ip
Gai

or
acy ALT
N ALE

‘=
=

Bi: Wet | LL
Lesa Nec
il! wie

tia
VX | :
Bae e
AR)
7 /

p ))

XD =
—, — 7.
S ’

Senn

———

Re
Av

Seeee™ NSS SN eaten A
\ AMAA Sis
A (Ss | \ Ree Tt
ik » Sin x H
KW Meats op:
HY Al \{ oS alts ‘ MN

POISON IVY Rhus radicans L.

1937 TEHON: ROUT THE WEEDS! 21

Control—In the case of Giant Ragweed, control measures
should aim to reduce the amount of ragweed pollen, prevent
seed production, and to destroy the plant as a weed. In either
case, efforts should be directed chiefly toward killing while the
plants are still young. The hard, woody stems of tall, mature
plants are difficult to cut. Young plants in fields and gardens
are readily killed by cultivation and hoeing. In waste places,
mowing as the weeds come into flower but before pollen is
produced will kill them. In fallow land, grassy plots and else-
where they can be killed easily by spraying with copper sulfate
or iron sulfate. Enforcement of weed-cutting laws in cities and
towns and the cutting of weeds on vacant land is important in
reducing the amount of pollen.

POISON IVY
Rhus radicans L.

Appearance-— Poison Ivy grows both as a vine and as a shrub.
Its outstanding characteristic is that each leaf is made up of 3
large separate leaflets, and because of this it often is called
Three-leaved Ivy. As a shrub Poison Ivy may grow 3 or 4 feet
high but usually is much smaller. It often is called Poison
Oak because of the resemblance of its leaflets to young oak
leaves. As a vine Poison Ivy climbs high on tree trunks, and on
fence posts and other supports. Its woody stem can be recog-
nized always by the short roots sent out in great numbers along
its sides, which attach it to the support. The stems bear
alternately placed, long-stalked leaves with irregularly lobed,
toothed, or sinuate margins. The end leaflet stands on a long
stalk, and the two side leaflets, the blades of which are unequal
at the base, stand on very short stalks. Clusters of small,
greenish white flowers are borne on stems 1 to 3 inches long
that grow out from the angles between leaves and stem. The
fruit is a greenish white, smooth, waxy, dry berry containing 1
small hard seed. A fruit cluster resembles a small currant cluster.
Both shrub and vine are perennial. They spread by creeping
rootstocks and are scattered extensively by multitudes of seeds.

Distribution—Poison Ivy is an American plant with a range
that extends across the continent from Nova Scotia to British
Columbia and southward to Florida and the desert regions of
the southwest. It grows throughout Illinois, being especially
abundant along fence rows and roadsides, where it generally

22

ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

/,

M y 2
| Uy Yj Yj Uf} Yj j Y
CAS Mt} o Li

1) Y Ylgg A
UY WJ GOLA

7,
Y
/
/

| Hien

A \ No SN
WAN WN
\

rn
ue

RAS

y
fr

», Z
hy /p_™
iG ju <
Cy Y/4 VV
GENT y
f) Cas

ff
Uff
h

——

——S
—-

-—_ —_
EZ ———

es

Was

==
SG

POISON SUMAC Rhus Vernix L.

1937 TEHON: ROUT THE WEEDS! 23

is seen as a shrub. But frequently in the borders of woods and
sometimes along fences it grows as a vine. It seldom persists
on cultivated ground, hence it does not often contaminate
agricultural seed.

Biology—Blossom time for Poison Ivy in Illinois begins the
latter part of May and extends well into July. The berries en-
large and ripen slowly, maturing from mid August to October.
They remain on the vines until late winter. Birds, especially
crows, eat them without harm and carry the seeds long distances.
Poison Ivy is important chiefly because all parts of it, but
especially the leaves and bark, produce an oleo-resin, toxico-
dendrol, which causes ivy poisoning. The plant is, quite justly,
feared by many persons, and little effort is made to eradicate it.
A few people apparently are immune, however, and it is possible
that many people poisoned by other plants blame Poison Ivy.

Control— The only satisfactory control for Poison Ivy is
eradication. Grubbing is sometimes necessary close to shrubbery
or trees too valuable to endanger by other treatment. Plowing
and cultivating fields and gardens keeps it under complete
control. Elsewhere chemical treatment gives most satisfaction
with least danger. Common salt solution, prepared by dissolv-
ing 3 pounds in 1 gallon of water and poured on the ground
around the plant kills the foliage. Or salt may be applied
dry. The first application should be made in early summer, and
later applications as new foliage appears, until the rootstocks
and roots have been starved to death. On agricultural lands
sodium chlorate is more satisfactory.

For ivy poisoning, the best advice that can be given is to
take all possible precautions to prevent poisoning. If poisoning
is suspected, immediate washing of all exposed parts of the
body with soap and water, followed by thorough rinsing with
clean water, is the best thing to do. After the rash appears,
several materials can be used to hasten recovery. But persons
severely poisoned should consult a physician and remain under
his observation until the poisoning has abated.

POISON SUMAC
Rhus Vernix L.

Appearance—Poison Sumac, often also called Swamp Sumac
and Poison Elder, is a shrub or small tree that grows usually
10 to 12, but rarely 25, feet high. Its stems are normally 2 to

24 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

3 inches in diameter, but on large specimens the trunk may be
as much as 6 inches in diameter. What are commonly called
leaves are but leaflets, and the 7 to 13 of them on one stalk form
a single leaf 6 to 12 inches long. The leaves occur alternately
on the twigs. The leaflet at the end of each leaf stands on a
distinct stalk, but the other leaflets are in pairs along the leaf
stem and are nearly stalkless. The leaflets are oval but they
vary considerably in shape and size, even on the same leaf.
They are green on both sides, pointed at both ends, and even
or somewhat wavy along the margin. The leaf stalk is somewhat
swollen at the base where it attaches to the stem. Clusters of
greenish white, very small flowers are borne on the current
year’s twigs on much branched stalks 3 to 8 inches long, which
arise in the angles between leaves and twigs. The fruit that
develops from these flowers is a small, greenish white, smooth,
shiny, waxy berry. Each fruit contains a single much wrinkled
or ridged seed. Poison Sumac is perennial and reproduces
entirely by seed.

Distribution Poison Sumac is a native American shrub. Its
natural range extends from Maine westward through Ontario
to Minnesota and south to Florida, Mississippi and Texas.
Throughout this region it is found only in bogs or boggy areas.
In the northern part of its range it is typically an inhabitant
of tamarack bogs. In Illinois it maintains this habit and conse-
quently occurs only in the northeastern corner of the state,
where it is abundant in the old tamarack bogs of Lake county.

Biology—The blossoms of Poison Sumac open in June. The
fruit ripens slowly, becoming mature in September, and clings
to the shrubs until winter. Of all the plants that grow in this
state, there is none so poisonous to the touch as Poison Sumac.
It is even more poisonous than its close relative, Poison Ivy.
Poisoning is due to a plant oil, known as toxicodendrol, which
is produced by the shrub in all its parts, but especially in the
bark and leaves. Exceedingly severe cases of ivy poisoning
develop on susceptible individuals who come in contact with
this shrub, but as with poison ivy there are some who apparently
are immune to poisoning.

Control—Control of Poison Sumac demands eradication, since
all parts of the shrub produce the poisonous oil that is responsible
for ivy poisoning. The only satisfactory eradication is to chop
down and destroy the stems or to poison the plant with chemi-

1937 TEHON: ROUT THE WEEDS! 25

cals. Although no experiments have been performed to show
the effect of chemicals on this shrub, undoubtedly it would be
possible to kill it with common salt by applying dry salt on the
soil around the crown of the shrub. Sodium arsenite could be
used also, probably with safety except where animals are
pastured, but sodium chlorate and calcium chlorate are to be
preferred because they are less poisonous to animals.

WILD PARSNIP

Pastinaca sativa L.

Appearance-—Wild Parsnip, in reality the cultivated or garden
parsnip escaped from cultivation, is a large coarse plant that
grows 2 to 5 feet high. Generally, its smooth, grooved and
ridged, coarse stem bears along its length a number of greatly
divided smooth leaves which have a distinct clasping arrange-
ment at the base. The stem ends in great heads of small yellow
flowers. Wild Parsnip is a biennial and the first year from seed
produces a very short stem, from which a rosette of leaves
spreads out on or near the surface of the ground. These leaves
are often 1% feet long, with long, grooved, flat leaf stalks and
blades very much cut up, closely and sharply toothed, and often
lobed. After the flowers wither, the fruit develops in the flower
heads at the top of the plant. Each fruit is composed of two
broadly oval, smooth, flattened halves, or seeds, about a quarter
of an inch long. Each seed is surrounded by a thin corky ridge.
Wild Parsnip reproduces entirely by seeds.

Distribution Wild Parsnip has been naturalized from Europe.
Apparently it has found this continent exceptionally favorable,
for it is now distributed to all parts of the United States and
southern Canada. The earliest known record of its occurrence
in Illinois is 1861, but undoubtedly it was here prior to that
time. It grows throughout the state and is an exceedingly
common weed everywhere, except in the extreme southern
part. Along roadsides, railroads, fence rows and on neglected
lands it is abundant, but is seldom seen on consistently culti-
vated land.

Biology—As a weed Wild Parsnip has some importance as an
inhabitant of meadows and pastures. It is of interest, also,
because some people, after coming in contact with it, develop a
skin poisoning quite similar to that received from poison ivy
and perhaps often confused with it. Although the root of the

26 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

y
7 BAA
YS Aes

434 F
Wee
ba as Hy ss ee 24
4 < y
PE. Q Hi Ws
SU SEAN

ae
YZ DS
|

7
yj —
yy Z L
d UL Wap
Wy (a Serr DO atl :
Uf ANS SSS
i - AN See >
IIL y SN) Sh
G = a

NV

g : ) N 4 (ans
i S : BA ‘“ VW UG}
f ny ? nd Wy i y Ui
i
Hl |/,

a YU IHR) A i
MO (> ie
\ NM Z
Q 1a |
S& Ny “x \
\

HORS CaS (1 AW Me

WILD PARSNIP Pastinaca sativa L.

1937 TEHON: ROUT THE WEEDS! 27

cultivated parsnip is not poisonous, that of the Wild Parsnip,
even though belonging to the same botanical species, is poison-
ous, even after it is cooked. The flowering period for Wild
Parsnip extends from very late May through late August in
Illinois, and seeding time from the last of July into October.
Seeds, produced in exceedingly large numbers, are widely
distributed by wind and water, but they are rarely contaminants
of agricultural seeds.

Control Although Wild Parsnip has found American en-
vironment suitable to its persistent spread, control and even
eradication is not hard. Because it is a biennial, this weed is
readily destroyed by persistent cultivation and is therefore
seldom seen on continuously cultivated land. For use in the
relatively neglected places where it persists, a number of simple
control methods are available. Chemicals such as iron sulfate,
sodium arsenite, and sodium manganate, are effective in the
eradication of this plant. Chlorates also may be used. Hand
pulling, early in the spring when the ground is soft, will bring
the roots out to such an extent that they do not reproduce.
Hoe cutting, so as to remove the leaves from the root crown,
if done in late autumn or early spring, is generally sufficient to
keep the plants from sending up flowering stalks. For plants
that send up flowering stalks, cutting while they are in blossom
will prevent the formation of seed and cause the plant’s death.

WHITE SNAKEROOT
Eupatorium urticaefolium Reich.

Appearance-— White Snakeroot, in some places known also as
White Sanicle and Deerwort Boneset, commonly grows 1 to
4 feet high. Its erect, slender and much branched stem bears
numerous nettlelike sharply toothed leaves, and ends in loosely
branched clusters of small bright white flower heads. The
large thin leaves, which are set in pairs on the stem and branches,
are smooth and pointed and have 3 main nerves that spread out
from the tips of the long slender leaf stalks. In the upper part
of the plant, the clusters of flower heads are borne also on stalks
which arise in the angles between leaves and stem. The clusters
generally are large, with branched and rebranched flower
stalks ending in heads of flowers about one-quarter inch broad,
and the tiny pointed flowers give the heads a fringed appearance.
The very small slender black seeds are 5-angled and topped with
a crown of fine white bristles. White Snakeroot, though it dies

28 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 23 AUGUST

Ss BAY \s = = ~ “ =
= LSS Ce =. LIF = =
ENV EL = 2 se
—> : Ve Se 2s
==> < E Sa E22
a 5 = =] > aap morale tee
=< = =! gS oe p> 2A LEE 2 fa-55
————S SS SS EAE yr FES Zz = Lede
> : REREZ IE pp =e 2 ‘
SjsSsSsseSsSS—SS=S—-S ace TO wate / -—- SQ OS
———ooeeeeSS SS BSE
—————— === a o Sc aa
= > S r
= Se
—— Ss ie —=—
Sea SS WS ’ , ; ae
——— FZZ WW,
=—=S>-= LE- SIS J
—————3 RSS eA Ys
aS EEZ °F WN
SSS =A Saw
———— EAB “STIS a
~~ 1)
SSSS-=z Way \
eS B
=

LESS
a — —S
——— ——
SSS —

SSS
——SSSSS
% SS =
\ SS SS

NN) pers f
1 1 |e 5S
Qa SEE
SS (Rey, Z yy
= end >, f
\gep | }
CAS
\\ Kd CEE \
== \4 Ze
Sy TAN i 7
\ \\W
\
\ \

\ Ry

it My)
Vitale

Eupatorium urticaefolium Reich.

1937 TEHON: ROUT THE WEEDS! 29

to the ground each winter, is perennial and comes up each year
from the wandering underground root for which it is named.

Distribution— White Snakeroot is a native plant. It ranges
naturally from Ontario southwestward to Nebraska and south-
ward to Georgia, Louisiana, and Oklahoma. Although it
originally inhabited rich woods, as a result of settlement and the
destruction of woods it now is found chiefly in moist fertile
soils in thickets and ravines, in open woods along stream banks,
and in wooded pastures. Infrequently it grows on hillsides and
on cleared but unbroken land, seldom in open sunlight. There
is no part of Illinois in which the plant is not found, although it
is rare in regions which originally were prairie.

Biology —Blossoming time of White Snakeroot in Illinois ex-
tends from about the middle of June well into October. Seeds
ripen the latter part of July and continue to ripen until frost
kills the plant. White Snakeroot is of no importance in culti-
vated fields but may be a dangerous plant in woodlands used
for pasture. Both cattle and horses, after feeding on this plant,
are affected with a disease known as “‘trembles.’’ Persons who
drink the milk of cattle that have fed on it are apt to contract
“milk sickness,’’ because of a poisonous material in the plant
known as trematol. Stock poisoning is most apt to occur when
pasturage is short or when a weed-infested pasture is over-
grazed. Toxicity of White Snakeroot plants varies in different
localities. Milk cows that feed on the plant show no symptoms,
because the poison is absorbed by the milk and discharged with
it, but when a cow goes dry it immediately becomes susceptible
to poisoning. White Snakeroot reproduces entirely by seeds.
One small flower head produces 10 to 30 seeds, and the number
that can be ripened on a single plant is very large.

Control Measures directed against White Snakeroot are
primarily for prevention of trembles and milk sickness. This
should involve eradication of the weed from all areas where
stock feed. Practically, the number of plants must be kept as
small as possible in pastures and woods where cattle and horses
graze. It is especially important not to permit these animals to
graze on infested land after about the first of July, since it has
been determined that the weed will kill stock that eat it when
it is about ready to blossom. Where White Snakeroot thrives
there will be little forage, and good timberland management
requires that such land should not be pastured. Milk from cows
feeding in infested pastures should not be drunk directly, but

30 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

NY,

",
D
UPrs
i
N
\

WS
\)

By

WS

Nuit

POKEWEED Phytolacca decandra L.

1937 TEHON: ROUT THE WEEDS! 31

there is little danger of milk sickness if such milk is sold to
dairies, so that it is mixed with large quantities of trematol-
free milk. Persistent use of scythes or cutting hooks keeps the
plant from going to seed, and this, repeated for several years,
will reduce White Snakeroot infestation on any land. In
timber tracts and ravines, where the soil generally is moist,
it is possible to pull up the plant, along with its entire shallow
root system.

POKEWEED

Phytolacca decandra L.

Appearance-—Pokeweed, very commonly known simply as
Poke and less frequently as Inkberry, stands at maturity 4 to
10 feet tall. Its red or purple tinted, stout, smooth and some-
times branched stem bears smooth deep green lance-shaped
leaves 6 to 12 inches long and ends in long upright shoots of
greenish white flowers. The alternately placed leaves stand on
short stalks, are pointed at both ends, and have no teeth on
their margins. The flower clusters, which at first are terminal,
become lateral because of continued growth of the stem and are
transformed into drooping shoots covered with short-stalked
dark purple berries. Each of the juicy berries bears about 10
seeds. Pokeweed, although it dies to the ground every year,
is perennial and lives over winter as a large underground root.

Distribution——Pokeweed is a native American plant with a
natural range extending from Maine westward to Minnesota
and southward to Florida and Texas. In Illinois it occurs in
every part of the state. It prefers fence rows, thickets and
waste ground in the country, and is a common plant of domestic
gardens and disturbed soil of all kinds in towns, cities and
villages. Although in America it is a dangerous weed, Poke has
been transported to Europe, where it is considered an ornamental
plant and is grown in gardens.

Biology—Blossoming time for Pokeweed begins during the
last of June in southern Illinois and in the early half of July in
northern counties. From this time on blossoms continue to
appear until the early part of September. Berries begin to
ripen 3 to 4 weeks after the blossoms first appear and continue
to ripen until late in November, when the above ground parts
of the plant are killed by frost. Pokeweed is relatively unim-
portant as a weed as far as cultivated fields and gardens are
concerned, and its seeds are not a common contamination in

32 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 23 AUGUST

_——_- -
Nos fy)

= e

}

RE SONY

i ee ‘ —
y bes.
\\ ‘

nt

NUTT = === S
a SX \“—CJittZ SS =
\ NEA EE FEE
ANAS NW

COMMON BURDOCK Arctium minus Bernh.

1937 TEHON: ROUT THE WEEDS! 33

agricultural seeds. Very young shoots from this plant are some-
times cut and eaten like asparagus. Both roots and berries
contain a drug, phytolaccin, and the berries, when eaten in
any quantity, cause severe nausea, and the roots are poisonous.
The mosaic disease of cucumbers and canteloupe attacks poke-
weed, causing a mottling of its leaves, and overwinters in its
roots. The berries are eaten to some extent by birds by which
the seeds are distributed widely.

Control—Since Pokeweed is perennial, to gain complete eradi-
cation it is necessary to kill the root. If the plants are numerous,
the roots can be grubbed out, dried, and sold to drug companies.
However, hoeing so as to cut the stem off below the crown gives
satisfactory control in gardens. Cultivation nearly always
disposes of the plant within a short time in fields, and the
danger from berries, which exists chiefly on neglected land, can
be greatly reduced by keeping the tops of plants cut down so
that berries do not ripen. For destruction of the roots in the
soil, which is particularly necessary near cucumber and cante-
loupe patches, the tops of plants should be cut off with a hoe or
spudding instrument, and then a chemical should be used. Either
common salt or sodium chlorate is very good for this purpose.
When Pokeweed occurs among other, more dangerous weeds,
the more drastic methods used on them control it readily.

COMMON BURDOCK

Arctium minus Bernh.

Appearance—Common Burdock, generally confused with the
larger but rarer Great Burdock, seldom exceeds 5 feet when
flower stalks are present. Its roughly hairy, stout ridged stem,
which springs from a great mass of very large wavy margined
strong-veined leaves, branches extensively near the top and
each small branch carries a cluster of moderate-sized purplish
or rarely white flower heads. Both the large leaves in the basal
clump and the smaller ones on the stem stand on stout hollow
leaf stalks, and are more or less heart shaped, light green above
and woolly beneath. The flower heads are globular and the
green part of the head below the purplish flowers is armed
with hooked spines, so that the flower head, later the seed head,
forms a prickly burr. The flat, oblong seeds are dull brown,
often curved, and have several lengthwise ribs. Common
Burdock is biennial. The first year it produces a large rosette

34 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 28 AUGUST

of leaves near the ground, and the second year sends up its tall
stem and flowers. It reproduces entirely by seeds.

Distribution “Common Burdock, like its near relative Great
Burdock, is a native of Europe that has become naturalized in
America. Since its introduction it has spread practically
throughout the United States and is, of course, found in every
part of Illinois. Records of its occurrence in this state ante-
date the Civil War. Although rarely persistent in cultivated
ground, it is common in neglected soil, along roadsides, in farm
yards and in pastures.

Biology.— The flowering period for Common Burdock begins
in late June in the southern part of Illinois and early July in
the northern part, and continues well into November, when
frost kills the upper parts of the plant. Seeding time begins in
September, when the flower burrs, which ripen late, begin to
produce ripe seeds. The ripened burrs remain closed on the
stalks throughout the winter. Both roots and seeds are used
to some extent in medicine; the roots, which are often 3 inches
thick and extend for more than a foot into the soil before
branching, are collected in theautumn of their first year. Cows
sometimes feed on the plant, and if they eat it in quantity they
yield bitter milk. Burdock seed, not a common contaminant
in agricultural seeds, generally is distributed in the burrs, which
catch on clothing or the fur or hair of animals or are transported
in Jate-cut hay. The two Burdocks, both weeds, are very
similar but can be distinguished readily since the leaf stalk of
Common Burdock is hollow, while that of Great Burdock is
solid.

Control Since the Common Burdock has such a long and
fleshy taproot that it cannot be uprooted after it has passed the
seedling stage, effort should be made to destroy seedlings as
they appear in the spring. Cultivating fields, hoeing small
gardens, and spudding out young plants in lawns and vacant
areas does this satisfactorily. In autumn, cutting the large
rosettes with a hoe or cutting off the second-year flower stalks
below the crown prevents seeding. Since the roots sprout
readily at the crown when plants are cut off at the soil line, it
is important to hoe deeply and also, whenever possible, to
treat each root with salt, waste tractor oil, or some effective
chemical.

Re
yy Hv haar? :

"\

Sa ao
aes ae:
iy i o-

nm
a i
{OIA aa

ley |
es
i]

CURRENT PUBLICATIONS
of the Illinois State Natural History Survey

A.—ILLINOIS NATURAL HISTORY SURVEY BULLETIN.

Volume 21, Article 1—The Effect of Petroleum-oil Sprays on Insects and Plants. By
M. D. Farrar. November 1936. 32pp, front + 21fig, bibliog. Contents: Foreword;
Properties of oil emulsions; Effect of petroleum oils on plants; Insecticide tests with
the emulsions; Oils with fungicides.

Volume 21, Article 2.—Responses of the Large-mouth Black Bass to Colors. By Frank
A. Brown, Jr. May 1937. 23pp, color front + 10 fig, bibliog. Contents: Problem of
color vision in fishes; Materials for the experiments; Training and responses of large-
mouth black bass; Interpretation of the responses; Summary. 25 cents.

B.—ILLINOIS NATURAL HISTORY SURVEY CIRCULAR.

26.—Insect Enemies of Peach in Illinois. By S. C. Chandler and W. P. Flint. May 1935.
38pp, 30 fig. Contents: Appearance and type of injury, control and life history of San
Jose scale, peach borer, lesser peach borer, shothole borer, peach-tree bark beetle,
terrapin scale, oriental fruit moth, peach-twig borer, plum curculio, tarnished plant
bug, stink bug, Japanese beetle, green June beetle, cotton-leaf worm moth, aphids,
grasshoppers, tree crickets, thrips. 25 cents.

27.—Windbreaks for Illinois Farmsteads. By J. E. Davis. April 1937. 17pp, front +
12fig. Contents: Planning the windbreak; Planting the windbreak; Care of the wind-
break; What the windbreak trees are like.

C.—ILLINOIS NATURAL HISTORY SURVEY MANUAL.

1.—Fieldbook of Illinois Wild Flowers. By the staff. March 1936. 406pp, color front +
349fig, index. Contents: Introduction; Key to families; Description of species (650).
$1.50.

Address orders and correspondence to the Chief

ILLINOIS STATE NATURAL HISTORY SURVEY
Natural History Bldg., Urbana, Ill.
Payment must accompany requests for publications, in the form

of U. S. Post Office money order made out to State
Treasurer of Illinois, Springfield, Illinois.

“ium

3 01